Soil penetrating electrode with conical taper

ABSTRACT

This disclosure describes a Soil Penetrating Electrode with Conical Taper for use with instrumentation for measurement of the electrical properties of soil in situ. The Electrode shape and configuration solves problems of stable and reliable contact with the soil, repeatable contact area, and ease of use by the operator.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

[0001] This invention was not made under any federally sponsoredresearch and development whatsoever.

FIELD OF THE INVENTION

[0002] The invention relates to the field of soil mechanics wheremeasurement of soil percent compaction and moisture content are requiredfor road beds and construction foundations. More particularly, theinvention relates to the measurement of soil electrical resistance andsoil electrical capacitance at a radio frequency, wherein an electrodeis used to connect the measurement instrumentation to the soil.

BACKGROUND OF THE INVENTION

[0003] There have been many applications wherein soil electricalproperties have been measured to determine geological characteristics ofsoils and earth structures in situ. Generally the electrode structurehas not been identified in the description of these inventions. U.S.Pat. No. 5,450,012, issued to Champagne, et.al. on Sep. 12, 1995,describes a Soil Electrode design that is claimed to be useful fordetermination the resistance of a volume of soil. Other prior artincludes U.S. Pat. No. 2,611,643 of R. V. Higgins, granted on Sep. 23,1952 that describes an automatic sprinkling device which includes twoelectrodes inserted into soil. U.S. Pat. No. 3,905,551 of Charles Aymede la Lachevreliere, granted on Sep. 17, 1975 describes a soilsprinkling device employing two electrodes, one lying in the uppersprinkled layer, and the other lying within the permanently moist layerat sufficient depth.

SUMMARY OF THE INVENTION

[0004] An object of this invention is to be able to make a repeatableand stable electrical contact with soil for measurement of itselectrical properties.

[0005] Another object of this invention is to be able to control thearea of electrical contact with soil for measurement of its electricalproperties.

[0006] Yet another object of this invention is to be able to make iteasy for the user to obtain repeatable and stable contact with soil formeasurement of its electrical properties.

[0007] The purpose of the Soil Penetrating Electrode with Conical Taperis to provide repeatable and stable electrical contact with soil for thepurpose of measuring the electrical characteristics of the soil at aradio frequency. When used with the Electrical Density Gauge, thepercent compaction and moisture content of the soil can be determined insitu from the measured electrical properties.

[0008] The Soil Penetrating Electrode with Conical Taper is made frommetal that is hard enough to be hammered into the earth or soil, yetductile enough to prevent shattering when hit. Typically, thecomposition of oil hardening drill rod is ideal for this application.The dimension of the Electrode is dependent upon the applicationrequirements, and this description is intended to show an electrodesuited to a typical application.

[0009] A conical shape has been designed for a soil penetratingelectrode that continually compacts the soil around the electrode as itis driven in. This continual compaction achieves excellent contact allaround the conical shape, and provides excellent control of the area ofcontact with the soil. Further to controlling the contact area, ashoulder is machined at the end of the conical taper that is undercut.When the conical electrode is driven in the soil to the level where theshoulder is level with the soil surface, a repeatable area of theelectrode is in contact with the soil.

[0010] If the electrode is driven farther into the soil, such that theshoulder is below the surface of the soil, the soil crumbs that may fallback in the cavity surrounding the undercut part of the electrode shaftmake a comparatively poor contact with the electrode. Consequently, anegligible change results in the functional contact area of theelectrode with the soil. Thus, the conical electrode shape that is thesubject of this invention assures positive soil contact andsubstantially constant contact area without the requirement for highlyaccurate placement with respect to the soil surface.

[0011] For this application, a 6 in. long Electrode is described, anddetailed in FIG. 1. The length of the soil electrical contacting area(2) of the Electrode is three (3) inches. For best accuracy it isdesirable that the total contact area be constant from measurement tomeasurement. It is also desirable that the Electrode be in intimate andtight electrical contact with the compacted soil. It is the object ofthis invention to solve the problem of constant electrical contact areaand also to solve the problem of intimate electrical contact with thesoil.

[0012] The contact area of the Electrode is machined to be a conicalsection that has a diameter of {fraction (3/16)} in. at the penetratingend (1), and a diameter of ½ in at the top of the contact area (3). Theconical taper is such that the spacing between the {fraction (3/16)} in.dia. location and the ½ in. dia. location is 3 inches. As the Electrodeis driven into the soil, the diameter of the hole continues to increaseeverywhere along its length, thus assuring intimate electrical contact.

[0013] At the ½ in. dia. location, a {fraction (1/16)} in. shoulder (3)is machined, which reduces the diameter of the Electrode to ⅜ in. Thisshoulder provides a visual reference to assure that the Electrode isdriven into the earth or soil, the full design distance of 3 in. Fromthat point a ⅜ in. dia. cylindrical section (4) is machined for theremainder of the total 6 in. length of the Electrode. This cylindricalsection provides a place to manually grip the Electrode while it isbeing driven into the soil, as well as a place to which electricalconnectors can be affixed.

[0014] The cylindrical section also provides an under-cut area, which nolonger has intimate electrical contact with the soil or earth. Even ifthe Electrode is driven slightly deeper than the 3 in. design depth, theintimate electrical contact area will still be only 3 in. long. And,should any crumbs of earth fall into the undercut area, the relativeelectrical contact with the soil will be very small when compared withthe tight electrical contacting area of the conical section

[0015] Lastly, a hole (5) is drilled transversely through the top areaof the cylindrical section of the Electrode through which a rod or nailcan be inserted to permit the electrode to be twisted as it is pulledfrom the earth or soil after use. This feature permits easy withdrawalof the Electrode, when driven into highly compacted soils.

BRIEF DESCRIPTION OF THE DRAWING

[0016]FIG. 1 is a side view drawing of the Soil Penetrating Electrodewith Conical Taper.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0017]FIG. 1 shows a drawing of the conductive metallic conical soilpenetrating electrode that is the subject of this invention. The point(1) of the electrode has been blunted purposely to prevent distortion ofthe metal when a rock is struck while placing the electrode.

[0018] The conical tapered area (2) of the electrode has a taper thatstarts at {fraction (3/16)} in. diameter and increases to ½ in. diameterover a 3 in. length. This small angle taper assures ease of driving theelectrode into compacted soil, yet serves to compress the soil aroundthe electrode over the whole length of soil contact.

[0019] The undercut shoulder of the conical electrode (3) is used as aguide for consistent soil penetration. The electrode is at the correctdepth when the shoulder is at, or slightly below, the surface of thesoil.

[0020] The undercut is {fraction (1/16)} in. to allow enough spacebetween the ½ in. diameter soil hole caused by the top of the conicalpart, and the ⅜ in. diameter electrode shaft (4). The ⅜ in. shaft istypically 3 in. long.

[0021] A hole in the top if the electrode shaft (5) is provided forinserting a nail or other metal rod to allow the electrode to be rotatedas it is withdrawn from the soil. In highly compacted and dry soils, itis difficult to remove the conical electrode because of the highcompaction pressures around the wall of the conical part. By twistingand pulling at the same time, this compaction pressure can be releasedeasily, allowing withdrawal by hand.

[0022] The conductive metallic soil penetrating electrode can be madefrom steel, stainless steel, bronze, or other metal with suitableelectrical conductance for the application.

[0023] The above description of the conical electrode includes typicaldimensions, which may change according to the soil type and applicationof this new electrode shape.

I claim as the subject of my invention:
 1. A conductive metallic soilpenetrating electrode for use in making an electrical connection withsoil for the purpose of measuring soil electrical parameters, that has along, small angle conical part that is in intimate electrical contactwith the soil.
 2. A conductive metallic soil penetrating electrodedescribed in claim 1 that has a shoulder that establishes the majordiameter of the conical part, said shoulder to be used as a gaugeshowing when the electrode has been driven to the correct depth into thesoil.
 3. A conductive metallic soil penetrating electrode described inclaims 1, and 2 that has a shaft that is undercut from the majordiameter of the conical part at said shoulder, said undercut preventingany loose soil particles that may fall in the hole from making asignificant change in the electrode contact area with the soil.
 4. Aconductive metallic soil penetrating electrode described in claims 1, 2,and 3 that has a hole drilled perpendicular in the undercut shaft intowhich a metal rod can be placed to allow the electrode to twisted tofacilitate removal from compact soils.